A study on the physiological parameters of corn during the jointing stage of growth under soil water stress based on the PSII light quantum yield (QY)

Abstract

Water stress is a major factor limiting corn production in the semi-arid and semi-humid regions of the world. Well-scheduled irrigation is necessary to increase seed yield and ensure yield stability in these regions. A reasonable and intelligent irrigation system is generally based on the measurement of soil water content or the monitoring of corn water demand. Therefore, it is vital to be able to quickly and accurately determine the optimal threshold of the physiological parameters of corn.

In this paper, in order to find the optimal threshold of the physiological parameters of corn, experiments in the open fields were conducted from February to June by measuring the corn growth under different degrees of water stress using remote sensing instruments. In this experiment, sweet corn 18# was chosen as the experimental subject, and several parameters of remote sensing spectral index such as leaf water potentia, Normalized difference vegetation index (NDVI), photochemical vegetation index (PRI), and PSII light quantum yield (QY) were measured at the same time every day-along with the varying moisture status—for the duration of the experiment. For this experiment, it was very important to set the varying moisture statuses as the moisture controlling standard. Leaf water potential and QY were selected as indexes to check the different moisture statuses. The QY proved to be sensitive to the water stress of corn and was chosen as the indicator. Furthermore, the effects on the corn under differing levels of water stress were explored by analyzing the variation trend of different remote sensing spectral indices. The main results and conclusions are as follows:(1) Differing degrees of water stress at the jointing stage of corn growth will cause the inhibition (in varying degrees) of leaf water potential, QY, NDVI, and PRI; and will also inhibit the processes of transpiration and photosynthesis. (2) After halting the water stress, with the different levels of water replenishment, the leaf water potential, QY, NDVI, and PRI will display the characteristics of the compensation phenomena. The compensation levels will depend on the degree of water stress. When the water stress is mild, all of the leaf water potential indexes, QY, NDVI, PRI will recover to normal levels or even succeed normal levels in a very short period of time-known as the super compensation effect. Meanwhile, for moderate levels of water stress, the compensation phenomena is also present; however, the replenishment of water cannot reach normal levels. Further, the water replenishment effect does not appear under conditions of severe water stress. This indicates that it is beneficial in maize growth for the corn to be under conditions of mild water stress.(3) Lastly, from the significance of the QY, water potential, PRI, and NDVI to water stress, it is apparent that the QY is the most reliable. Therefore, QY is the most reasonable choice to guide the water-saving irrigation in irrigated farming areas.